Avoiding Lub Oil Fires

TERRY COOPERFM GLOBAL

D uring the period 1988-2003, a sampleof 23 companies in the utility, cogen-eration, and pulp and paper industriesexperienced catastrophic f iresinvolving turbine oil systems. The compa-nies that included 19 power plants with tur-bines ranging from 40 to 820 MW sufferedan average property damage of $24 million(indexed to todays dollars).

The mean outage due to the fires waslonger than six months. Lost generating capac-ity was in excess of 20 million MWh, withthree units having to be retired prematurely.

Fires in 17 of those units could have beenavoided if proper precautions and fire safetymeasures had been taken. The remaining sixfires were in facilities whose management initi-ated some simple, low-cost protection measures.The average property damage in the latter caseswas about $900,000. The mean outage time: lessthan two weeks. What did these six companiesdo that was different from the other 17?

Protect your companyTake a moment and visualize where your com-panys turbines are located: the exterior designof the buildings where theyre housed, the inte-rior layout, and the floor plan. Think aboutwhat it cost to build those facilities, how muchis spent to operate them, and how much rev-enue those turbines generate for your company.

Now imagine what would happen to yourfacilities if lube oil, under pressure, suddenlysprayed from the turbines onto a hot surface near-by and sparked a fire. If you are an upper-levelexecutive, here are some questions to consider: How likely is the possibility of a lube oil firein my facility? What risk does this pose to my companysbottom line? How will this affect my companys overalloperations? How could it affect our market share?

If you are a mid-level manager, consider: How much heat and smoke would such a fireproduce? How would the fire behave? How much damage would it cause to my tur-bine and to the entire facility? What would it take, and how long would ittake to put out that fire? Do we have the proper protection to extin-guish such a fire and protect our business?

Test resultsIn early 2004, FM Global (www.fmglobal.com), a commercial and industrial propertyinsurer, conducted a series of 23 tests to

assess the fire fighting arrangements in tur-bine halls. The study examined the impact ofvarious sprinkler configurations againstpotential hazards associated with turbinehalls in power generation plants that have nooperating floors. [1]

Under a movable ceiling [2] inside a firelaboratory at the FM Global ResearchCampus,West Glocester, Rhode Island, engi-neers constructed a large-scale mockup of aturbine hall, consisting of a lubeoil tank, tankcontainment area, and the high- and interme-diate-pressure sections of a turbine located ona pedestal. That pedestal alone measured 15ft. (4.5 m) wide x 20 ft. (6.1 m) long x 18 ft.(5.5 m) high, with a grated walkway extend-ing along one edge.

The objectives of the study were to: Provide detailed visual documentation ofthree potential fire scenarios Examine new and existing protectionschemes to mitigate fire losses

Three different fire hazards were exam-ined in the study: Spray fires the result of oil being releasedunder high pressure, causing a spray effect Pool fires the result of oil accumulating,in depth, on a floor or in a contained area Three-dimensional spill fires the result ofoil leaking under low pressure, cascadingfrom an elevated surface to a lower surface,and igniting along the way

The fuel source for each of these tests wasa standard mineral oil with a flash point of285 F (140 C) and a 20,000 BTU-per-pound output. Once ignited, this particularlube oil burns like gasoline.

The tests produced some surprisingresults and gave some valuable lessons.Spray fires cannot be extinguished by ceilingsprinkler protection. A high-density, localapplication sprinkler system [3] (water spraysystems or deluge systems) will control thefire, but a multiple approach is needed tominimize the damage.

Pool fires, it was found, can be extin-guished by ceiling-based sprinklers, butsprinkler density and ceiling height deter-mine whether or not this happens. Thegreater the distance between the sprinklerand the fire, the greater the water densityneeded to put out the flames. If there is alarge distance and a low water density, thesprinkler system will be ineffective.

Three-dimensional spill fires, much likespray fires, cannot be extinguished by ceilingsprinklers. Properly designed local applica-tion sprinkler systems [3] will control the fire.A multiple approach is needed to minimizedamage to your facility.

Immediate action

Shut oil off safely Contain and drain the oil Have an emergency response plan in place Install properly designed sprinkler systems

The first three of the above are measuresthat any company can take right now. In theevent of a turbine lube oil fire, its necessaryto terminate the oil flow as quickly as possibleto stop feeding the fire. However, immediate-ly stopping the flow of lubricating oil canresult in costly damage to the equipment.

Therefore shut-down procedures shouldbe designed based on your site-specific con-ditions. They could take anywhere from 20 to45 minutes. During this time, you should alsohave a means of containing and drainingthe leaking oil from the fire area to removethe fires fuel source. To contain an oil leak,companies should apply shields at potentialoil spray leak points in the lube system andinstall curbing where necessary to stop thespread of leaking oil.

By draining leaking oil to a safe contain-ment area, the fire risk is minimized becauseyoure removing a potentially volatile fuelsource. And, of course, make sure your compa-ny has emergency response procedures in placeand that all employees are trained in these pro-cedures. Hold indepth consultations withexperts in fire sprinkler system technology toselect a sprinkler system for your facility.Long-term measuresIn addition, companies and turbomachinery-operators should see to it that the followingmeasures are taken to prevent or mitigate theconsequences of these fires: Use welded pipe construction whereverpossible Only use flanged and threaded pipe con-nections to help in maintenance work onequipment such as bearings, pumps, filtersand heat exchangers, and final terminationsfor instruments Consider using stronger, cleaner stainlesssteel pipe, tubing, and fittings instead of car-bon steel Use guard piping [4] design concepts wher-ever possible to incorporate supply pipingwithin the return piping Insulate against dissimilar material contactat terminations Avoid excessive vibrations [5]. They cancause mechanical fatigue and consequent fail-ure of the pressure boundary.

Examples of vibration problems areloosening of bolts and nuts at flangedjoints, failure of threaded joints at valvesand pressure gauges. Failures at socketweld (root valves where the valve and nip-ple assembly have been used to support apressure gauge) can produce a cantileveror pendulum effect

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Avoiding lube oil firesCARE AND PRECAUTIONS CAN PREVENT CATASTROPHIC DAMAGE

www.turbomachinerymag.com24 Turbomachinery International January/February 2005

www.turbomachinerymag.com

Lock drain valves in the closed position onreservoirs, storage tanks, and conditioningequipment Prevent released oil from contacting ignitionsources by providing proper electrical enclo-sures and spray shields at flanges to direct thestream away from hot components Ensure proper maintenance proceduresusing documented, approved procedures andqualified personnel Avoid breeching the pressure boundary whenthe system is in service (for example duringfilter changing unless extreme caution andisolation are provided) Flush or purge residual oil from the systemprior to any hot work Ensure vessels are vented to locations thatare free of ignition sources Consider using checklists. This ensures thatsystems that are dismantled for maintenanceare properly reinstalled before returning toservice Consider using a less flammable oil

Various types of lube oil are used with tur-bomachinery equipment; some are less flam-mable than others. In the coming year, FMGlobal plans to evaluate less flammable fluidsunder specific power generation operatingconditions and study the possibilities of suit-able alternatives to fixed fire protection sys-tems in power generation facilities.

Footnotes[1] In some turbine buildings, the turbine itself islocated on a solid floor while other equipment is

located in a separate room beneath that floor.[2] A movable ceiling is one that can be raised orlowered from 10 ft to 60 ft to test fires in differentstorage sized facilities[3] Local application sprinkler systems are cus-tom-designed to protect specific types of equipmentby providing a water source closer to the targetedarea than ceiling sprinklers. These units are oftenbuilt to surround the equipment with sprinklerheads mounted above, around, and below.[4] Guard piping is a pipe within a pipe. Like adouble-hulled ship, the guard piping prevents therelease of the fluid running inside the inner pipe ifit is cracked or damaged.[5] Vibration can be reduced by mounting instru-ments on racks, providing flexible metal hosedesigned for the service, using snubbers in sens-ing lines to dampen hydraulic shock, providingadditional support on main lines and correctingany rotating equipment imbalance.

AuthorTerry Cooper is assistant vice president andpower generation industry engineering leader forFM Global, a leading commercial and industrialproperty insurer. He has 31 years of experiencein the power generation industry, working for apower generation utility, as a consultant, andwith FM Global. Cooper is an active member onseveral committees of the American Society ofMechanical Engineers (ASME) and is a pastchair of the ASME Power Divisions TurbineGenerators and Auxiliaries Committee.

January/February 2005 Turbomachinery International 25